The present invention relates generally to the field of alternators as used, for example, to supply DC electrical power to motor vehicles and, more particularly, to an improved alternator having a rectifier bridge assembly contained within the alternator housing.
A three phase alternator rectifier bridge, such as used in a motor vehicle alternator, comprises three "negative" diodes having their anodes connected to a ground terminal and three "positive" diodes having their cathodes connected to a voltage output terminal. Each of the cathodes of the negative diodes are connected to one of the anodes of the three positive diodes and to one of three stator windings of an alternator. In the interest of conserving space and facilitating the manufacture and repair of alternators, the diodes used to form rectifier bridge circuits have been packaged together as a unit which preferably is mounted within the housing of the alternator. For example, U.S. Pat. No. 3,184,625 describes a technique for mounting diodes on metal plates within the housing of an alternator. The metal plates provide electrical interconnection to common terminals for each set of diodes. However, numerous wire-to-wire solder connections are required to interconnect the diodes in the rectifier unit.
Compact packaging of a rectifier creates a problem in connection with the dissipation of heat which is generated by the conduction of substantial currents through the diodes of the bridge circuits. U.S. Pat. Nos. 3,539,850, 3,925,809, 3,959,676, 4,218,694, 4,307,437, 4,321,664, 4,538,169, 4,799,309 and 4,835,427 all show various techniques for packaging diodes in a manner that will facilitate heat dissipation. In particular, U.S. Pat. No. 3,959,676 describes sandwiching the diodes between a pair of heat sinking DC terminal plate members and a generally U-shaped circuit board member comprised of conductive strips embedded within and insulated by a plastic material. The resulting unitary composite body is mounted within the housing end plate of an alternator. U.S. Pat. No. 4,538,169 describes another sandwiched diode structure wherein a base is mounted on the alternator housing case to transfer heat directly thereto.
Commonly owned U.S. Pat. No. 5,043,614 describes an alternator having a rectifier bridge mounted to the exterior of the alternator housing. Such a configuration has the desired characteristic of being easily manufactured and has rapid dissipation of heat. Packaging flexibility is limited with such a design because the rectifier bridge limits space that would otherwise be available for mounting the alternator to the engine. Because of the decreasing underhood space in automobile designs, providing an alternator with packaging flexibility is increasingly desirable.
It is therefore desirable to provide an alternator design which combines the advantages of packagability, manufacturability and cost while maintaining good heat dissipation.